Not flaming meteorites, not an ice age; this is what really killed the dinosaurs. Tired of being one-upped constantly by LMB, its rivals traveled back in time so that they could get a headstart on their ads. Unfortunately, to the detriment of dinosaurs everywhere, they traveled back a bit too far.
Weakened with a strange skin affliction called 'state-pox', the T-rex is in the final throes of death. It looks longingly at the sky, wishing a meteor would take it out painlessly. No meteor ever arrives. Thus ends the reign of the dinos -- not with a bang, but with a flash... a flash ad.